International Symposium on Cereal Leaf Blights 2019 | University College Dublin, Ireland | 22-24 May 2019

Low amplitude boom-and-bust cycles define the septoria nodorum blotch interaction


Huyen Phan Phan
Curtin University
CCDM

Darcy Jones
CCDM
Curtin University

Kejal Dodhia
CCDM
Curtin University

Fran Lopez Ruiz
CCDM
Curtin University

Marc-Henri LeBrun
Bioger
INRA

Patrick Brunner
ETH

Richard Oliver*
Curtin University

Kar-Chun Tan
CCDM
Curtin University


Poster Presentation
Evolution and Population Biology

Atrium, UCD O'Brien centre for Science
Poster 5

View this abstract online by visting isclb2019.com/see/ABS58124

Septoria nodorum blotch (SNB) caused by Parastagonospora nodorum is a major disease of wheat Western Australia and has been a major target for breeders for many years. We assembled a panel of 155 WA P. nodorum isolates collected over a 44-year period and compared them to 23 isolates from France and the USA using 28 SSR loci and to a large global population using 5 SSRs. The WA P. nodorum population could be divided into five groups with contrasting spatio-temporal distribution and different reproductive modes.

The majority of the WA isolates fell into two groups that were found throughout the collection area and had balanced mating type allele frequencies consistent with regular sexual reproduction. The other three groups were found in restricted locations, were transient and consisted of a single mating type consistent with asexual reproduction only.

The asexual groups coincided with the adoption of only a single or a small group of wheat cultivars. When introduced, these cultivars had high scores for SNB resistance but declined over subsequent seasons until replaced with new more resistant varieties. The asexual populations were more pathogenic on contemporary cultivars than the co-existing sexual populations.

The asexual populations was studied by comparing them with the sexual populations and a large group of overseas isolates and were found to be more closely related to overseas population consistent with  regular invasion into WA despite the extensive biosecurity precautions.

The study has an important practical outcome as it can be used to define a rational method to select isolates to be used when testing the resistance of cultivars being trialled for release. To optimise this process, it is important to select both current most virulent isolates as well as examples of sexual populations. The implications of this study for this and related pathosystems will be discussed.